INITIATION, LOCALIZATION, AND GROWTH OF NODULES WITHIN THE ROOT SYSTEM OF PEA AS AFFECTED BY ASSIMILATE AVAILABILITY

摘要

The effect of carbon nutrition on pea nodule growth was investigated in two experiments either by modifying C availability (using plant shading) or by modulating competition for C between nodules and other plant organs using contrasted nodulation conditions (produced by inoculating at weekly intervals from radicle emergence, which resulted in various shoot and root developments). Another treatment in which plants were grown with 14 mol m~(-3) as N in NO_(3~-) served as a control for maximal root development (as this nitrate dose totally inhibited nodulation) and for maximal N supply. Plants were grown in hydroponics in a greenhouse with a mean temperature of 20 deg C. They were harvested at two- or three-day intervals during the whole vegetative period. The taproot was divided into 2-cm long segments for morphological observations, which included the number and maximal length of lateral roots as well as the number and biomass of nodules on the taproot segment and its lateral roots. The plants weredivided into several parts (sowed seed, shoot, roots and nodules) that were weighed separately and ground for determination of their N content.